US 8148669 B2
The present invention provides an apparatus and method for effectuating temperature control in roller grill assembly. Some embodiments provide a roller grill assembly which provides enhanced measurement by utilizing temperature probes located in convective air streams generated in the roller tube. Certain embodiments also provide an improved method for maintaining of a food product temperature by utilizing an intermediate holding mode. Finally, certain embodiments provide improved current control by limiting the number of heating circuits of a food heater that may be simultaneously enabled such that the current draw does not exceed a maximum current draw.
1. A roller grill assembly, comprising:
a plurality of roller tubes, each roller tube rotatably mounted to the housing, wherein each of the plurality of roller tubes is substantially hollow and defines a first opening at a first end of the roller tube and a second opening at the second end of the roller tube, and wherein each of the plurality of roller tubes includes a heating element for heating a surface of the roller tube;
a first restrictor positioned orthogonal to a first opening at a first end of the roller tube, the first restrictor substantially covering each of the first ends of the plurality of roller tubes, wherein the first restrictor does not contact the first ends of the plurality of roller tubes;
wherein the first restrictor creates a convective air stream within each of the roller tubes when the heating element is activated; and
a plurality of temperature measuring probes located within the hollow portion of at least one roller tube of the roller grill assembly to measure the temperature of the convective air stream within the associated roller tube.
2. The roller grill assembly of
3. The roller grill assembly of
4. The roller grill assembly of
5. The roller grill assembly of
6. The roller grill assembly of
7. The roller grill assembly of
8. The roller grill assembly of
9. A roller grill assembly, comprising:
a plurality of roller tubes, each roller tube rotatably mounted to the housing and rotatably driven by a motor apparatus;
a plurality of heating elements associated with at least one of the roller tubes for heating the roller tube;
wherein the plurality of roller tubes are separated into independent cooking zones to permit temperature selection and control within each cooking zone; and
at least one measuring probe positioned in the air stream of the roller tubes and approximate an end of the roller tubes and not in contact with a surface of the roller tubes.
The present invention relates generally to cooking assemblies, and more particularly, to an apparatus and method for effectuating temperature control in roller grill assemblies.
In conventional roller grill assemblies, an array of roller tubes are rotatably mounted within a housing. Each roller tube may be heated, providing that the heat is then transferred to food placed on the roller tubes.
One drawback of a conventional roller grill assembly is the temperature variance along the length of the roller tubes. A single, homogeneous heating element running along the length of a roller tube generally results in hotter tube surfaces at the middle of the roller tube than at the distal, or outer, ends of the roller tube. Thus, food positioned toward the outer ends of the roller tubes are not heated to the same temperature as food positioned near the middle of the roller tubes. The differences in heating temperatures results in uneven cooking of the food products. Other devices attempt to address this issue by utilizing variable heating elements, or even multiple heating elements. These devices allow for controlled variations of the heating element wattage along the length of the roller tubes. However, these designs also increase the complexity of the device, and thereby increasing the cost, and fail to entirely solve the problem.
Surfaces of the roller tube, near the ends of the tubes provide the most convenient location to mount one or more temperature probes. This configuration results in measurement of a temperature that is inherently offset, or skewed, from the actual temperature of the food products. The temperature skew, or offset, is a direct result of the delay when measuring heat transferred from the food, then to the roller tube surfaces, and finally to the temperature probe through the surface and mounting bracket for the temperature probe. Therefore, the measured temperature is time-delayed based on the time required for the various parts of the system to reach a temperature equilibrium, which rarely happens. As a result, the correlation between the food temperature and the probe-measured temperature is adversely impacted.
The potential to undercook or overcook food due to the wide temperature variations along both the length of the roller tube and over time. The aforementioned delay in translating the temperature variations quickly to the temperature probe makes it difficult to precisely control the heating elements. Therefore, heating elements are frequently turned on too late, or may stay on for too long of a period to maintain a consistent temperature. Therefore, conventional methods of measurement and control are unable to respond accurately and quickly to these temperature variations.
Some conventional roller grill assemblies provide a control that cooks food products initially, while then switching to a hold mode to maintain product temperature at a safe level. The holding temperature is set lower than the cooking temperature to prevent the food products from overcooking, while also maintaining a safe temperature for holding the food. This holding temperature ensures that the quality and safety of the food products over an extended period of time. However, when a conventional roller grill assembly switches from a cook mode to a hold mode, the food products on the roller tubes tend to drop in temperature faster than the measurement probe can detect due to the exposure of the food products to the ambient air and the aforementioned equilibrium delay. This results in food products that may drop below a safe holding temperature for a period of time before the holding mode raises the temperature of the food products above that threshold.
A conventional roller grill assembly may also provide a warming area for related food products, such as a bun warmer for hot dogs. However, the heating of both a series of roller tubes and a warming area can result in a substantially higher current draw than a roller grill assembly without a warming area. This higher current draw requires an end user to provide a larger electrical circuit for powering the roller grill assembly, which can significantly increase the cost of installing such a system and is inefficient since the peak current draw tends to be much higher than the average draw.
Furthermore, roller tubes of a conventional roller grill assembly are generally provided with a smooth finish. However, after the fatty oils of a food product are released during the cooking process, the oils have a tendency to adhere to the outer surfaces of the roller tube. These oils decrease the friction between the roller tube and the food products, which results in food products fail to rotate due to the undesirable slipping of the product on the tubes. Food products that are not evenly turned may cook unevenly and, in certain circumstances, may fail to even reach a safe temperature.
In view of the foregoing, there exists a need for a roller grill assembly that provides more accurate and responsive heating temperature control than the prior art systems. There also exists a need for a roller grill assembly that provides even and effective heating along the entire length of the roller tubes. Additionally, there exists a need for a method of limiting current draw in different heating areas of a roller grill assembly, such as a cooking area and a warming area, enabling the use of smaller electrical circuits for operation. Furthermore, there exists yet another need to provide improved surfaces for roller tubes in a roller grill assembly, to prevent undesirable sliding or slipping of the food products. The present invention addresses these needs.
The present invention provides an apparatus and method for effectuating temperature control in roller grill assemblies. In one disclosed embodiment, a roller grill assembly comprises a housing; and an array of roller tubes, rotatably mounted with the housing. A convective air condition is created within each roller tube, when the roller tube is heated. Probes are mounted in the air streams of the array of roller tubes, the probes adapted to measure heating temperature of the roller tubes.
One aspect of the present invention provides a roller grill assembly having a housing and an array of a plurality of roller tubes. Each of the roller tubes is rotatably mounted to the housing and is substantially hollow. Each roller tube defines a first opening at one end of the roller tube and a second opening at a second end of the roller tube. Furthermore, each roller tube is provided with a heating element coupled thereto, which heats the outer surface of the roller tube. Additionally, a restrictor is placed in close proximity to the first opening of the roller tubes such that the restrictor substantially covers each of the first ends of the roller tubes and generates a convective air stream within each roller tube.
In some embodiments of the present invention, a plurality of measuring probes are located inside one or more of the roller tubes. Preferably, at least two measuring probes may be provided in a single roller tube and used in combination to determine the temperature of the roller tubes. Furthermore, in some embodiments the roller tubes are positioned at one or both ends of the hollow roller tubes, and preferably near the central axis of the roller tube away from the outer surface to improve measurement readings.
In some embodiments of the present invention, the roller tubes of the roller grill assembly may be divided into one or more heating zones, such as a first heating zone and a second heating zone. In these embodiments, it is contemplated that the one or more heating zones may be individually controlled.
Another aspect of the present invention provides an improved method for maintaining food product temperature in a food heater, such as a roller grill assembly. This method begins by exiting a cooking mode, which cooked the food at a cooking temperature. After the cooking mode, an intermediate holding mode is entered. In the intermediate holding mode, the food heater attempts to maintain the food product at an intermediate holding temperature for an intermediate holding time period. The intermediate holding temperature may be the average of the cooking temperature and a final holding temperature while the intermediate holding time period may be a fixed time, such as 10 minutes. The intermediate holding mode may require setting the intermediate holding temperature and intermediate holding time. As long as the intermediate holding time has not elapsed, which terminates the intermediate holding mode, a measured temperature is compared against the intermediate holding temperature. If the measured temperature is less than the intermediate holding temperature, a heating unit of the food heater is turned on. On the other hand if the measured temperature is greater than the intermediate holding temperature then a heating unit of the food heater is turned off.
Another aspect of the present invention provides a method for improved current control in a food heater having multiple heating circuits. According to this aspect of the present invention, embodiments may be provided with multiple heating circuits, each individual heating circuit drawing a certain amount of current when enabled. Furthermore, a maximum total current draw is provided, where a individual heating circuits can only be enabled if the individual current draw of the heating circuit plus the individual current draw of each of the enabled heating circuits is less than the maximum current draw. In some embodiments, certain heating circuits may be given a higher priority level than other circuits, such that lower priority heating circuits may be disabled to enable a higher priority level heating circuit if enabling both circuits would exceed the total current draw. Such an aspect is especially applicable to a roller grill assembly, such as one having one or more array of roller tube heating circuits and a warming oven, or area, heating circuit.
The following description and drawings set forth in detail a number of illustrative embodiments of the invention. These embodiments are indicative of but a few of the various ways in which the present invention may be utilized.
A more complete appreciation of the present invention is provided by reference to the following detailed description of the appended drawings and figures. The following description, in conjunction with the appended figures, enables a person having skill in the art to recognize the numerous advantages and features of the present invention by understanding the various disclosed embodiments. The following figures are utilized to best illustrate these features:
The following discussion is presented to enable a person skilled in the art to make and use the present invention. The general principles described herein may be applied to embodiments and applications other than those specifically detailed below without departing from the spirit and scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments expressly shown, but is to be accorded the widest possible scope of protection consistent with the principles and features disclosed herein.
Referring first to
Referring now to
The roller tube 104 may be manufactured using any one of various materials known to be useful for conducting heat to a food product while generally maintaining a desired temperature. One example is a roller tube 104 constructed from a metal coated with a material with a low coefficient of friction, such as polytetrafluoroethylene, commonly known by the trade name Teflon®. The low-friction coating makes the roller tubes 104 easy to clean in a commercial application. Each roller tube 104 may be constructed to have any desired length and diameter. A roller grill assembly 100, as shown in
Each roller tube 104 may be optionally provided with a sprocket 210 attached along an outer perimeter of the roller tube 104, generally at one of the respective ends 202 or 204. Looking at
Referring back to
As the heating element 212 heats the air inside the roller tube 104, the air has a tendency to expand and flows out of the ends of the roller tubes 104 as depicted by arrows 216 shown in
Embodiments of the present invention provide a more even distribution of the heated air by utilizing controlled, convective air streams which are created within each roller tube 104. In one embodiment of the present invention, one or both ends of the roller tube 104 may be restricted, although each restriction can be to varying degrees.
In some embodiments, a second end cover 219 may be provided to cover all or part of exposed components on the second side 222 of the roller grill assembly. The second end cover 219 may be manufactured of any material that is suitable for use in a roller grill assembly to provide a general enclosure to cover the operating components. Ideally, this second end cover 219 would not absorb the majority of the heat of the roller grill assembly so it would be safer for general use and to prevent combustion of any products in close proximity. However, the second end cover 219 does not generally affect the flow of the air through the roller tubes 104 in any significant way.
The first side 220 of the housing 102 of the roller grill assembly also has several exposed components. In particular, each of the roller tubes 104 is exposed at the first side 220 of the housing 102, and therefore the second opening 208 of each roller tube 104 is exposed. In embodiments of the present invention, a restrictor plate 218 is placed in close proximity to the end of the series of roller tubes 104 to restrict the flow of air out of the roller tubes 104 through the opening. In particular, the restrictor plate 218 may be placed as little as 2 millimeters away from the second opening 208 of the roller tubes 104 or as much as several centimeters away. The restrictor plate 218 restricts the flow of air out of the tube, and in turn creates a convection effect as a natural result.
Other embodiments also anticipate that the restrictor may incorporated into the roller tubes. For example, an insert may be used to cover part of the opening at one or both ends of the roller tube. Furthermore, it is also contemplated that a restrictor plate may also be used at the second end of the housing 102 depending on the desired configuration. The various convection effects resulting from configurations having different temperatures, different roller tube diameters, and other adjusted variables may be more desirable for a particular application. Therefore, the present invention is intended to embody all such configurations that are commensurate with the spirit of the particular embodiment described with respect to
By applying restrictions to the openings of the roller tubes 104, a natural convective air stream is provided throughout each roller tube 104, reducing the temperature variances along the length of the roller tubes 104. The convective air stream may also be created by utilizing external forces, such as a fan, a baffle, or other mechanical means, which may be referred as forced convection. Other methods may also be applied to create convective air streams throughout each roller tube 104 without departing the scope and spirit of the present invention.
Another aspect of the present invention is the mounting of temperature probes in certain embodiments. Temperature probes are mounted to measure the heating temperature of the food products. Thus the temperature probes are used to control the heating element 212 depicted in
In the embodiment depicted with respect to
Mounting temperature probes in air streams to measure heating temperature of a roller grill assembly is more advantageous compared with conventional methods which tend to indirectly measure the outer surface of the roller tube by mounting the temperature probe onto a sheet metal bracket that generally center the heating element of the roller tube. As a result, the conduction and dissipation of heat to outside influences creates a measurement error. Therefore, the conventional methods provide less accurate measurement of heating temperature of a roller grill assembly. Comparatively, the embodiment in
The depicted embodiment may use two probes in the same roller tube, such as probe 224 and probe 226 in roller tube 104D to average the temperature in the tube. In particular, temperature data such as temperature differences, average temperature, and weighted average temperature, may be calculated by using the pair of probes 224 and 226. Again, this temperature date may be used to provide more accurate control of the roller grill assembly. This further results in faster temperature recovery plus a more even heating temperature across the surface of the roller grill. In some embodiments, including the calculations from probe 228 and probe 230 may further increase the ability to accurately control the roller grill assembly when a single temperature is desired across the entire surface. However, in other embodiments, probe 228 and 230 may be used to measure and control the lower half of the roller grill assembly to provide a different temperature than the upper half of the roller grill assembly.
Looking now at
The first heating zone 240 and the second heating zone 242 may have different temperature requirements. Therefore, having probes 224 and 226 in a different zone than 228 and 230 allows the temperatures of the respective heating zones 240, 242 to be controlled independently. Furthermore, it is possible for one heating zone 240 to be used to cook food products while a second heating zone 242 is used only to hold food products at a serving temperature. Obviously, a person having ordinary skill in the art would recognize that this configuration can be further modified to add additional probes and additional heating zones as desired.
It is desirable in nearly every roller grill assemblies or other food cooking device to maintain food products at or above 140 degrees Farenheit for safety reasons. After cooking a food product, many conventional roller grill assemblies switch from a cooking mode to a holding mode to prevent overcooking of the product, but to maintain a safe temperature. Therefore, this switch from one mode to another means lowering the operating temperature of at least some of the roller grills of a roller grill assembly. A conventional method for achieving the process is best explained with reference to
The “conventional hold mode” 800 depicted in
Therefore, embodiments of the present invention provide an “advanced holding mode” 900, the flowchart of which is depicted in
The method described with respect to
Looking first at
Finally, another aspect of the present invention is the current control aspect, allowing for lower rated circuits to be used to power the roller grill assembly. In a conventional roller grill assembly with a warming tray, there is a current draw associated with each heating zone or the roller tubes and the bun warming area. This may force end users to use a larger-capacity circuit than desired or available. The present invention provides embodiments of a roller grill assembly, such as the roller grill assembly 100, which are configured such that the warming tray 108, depicted in
According to the current-control aspect of the present invention, embodiments may be provided with a current control circuit in the roller grill assembly. The current control circuit may check to determine which relays are providing current to a particular set of roller grill tubes 104 or the warming area. For example, if the roller grill array is divided into two heating zones as depicted in
The previous description of the disclosed embodiments is provided to enable those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art and generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.